We’re all 17th cousins, aren’t we?

But it seems Benedict Cumberbatch’s uncanny resemblance to his subject may be down to more than just good acting…because it turns out they are related.

The actor, 38, is a distant cousin of the celebrated mathematician, who broke the German Enigma code during World War Two.

Both men share a common 15th century ancestor, John Beaufort, the Earl of Somerset, making them cousins 17 times removed on his father’s side, experts from the genealogy website Ancestry said.

Somewhere in the back of my mind I’ve got the idea that by the time you reach 12th or 13th cousins then certainly near all Brits meet that and by the time we reach 16th we’re getting towards all human beings, aren’t we?

OK, maybe not the Andaman Islander and the Finn but there is some point where “cousinry to the nth degree” includes most of humanity, isn’t there?

24 thoughts on “We’re all 17th cousins, aren’t we?”

  1. Exactly. With every generation, you go back, you double the number of ancestors. OK, There’s going to be some inbreeding in local areas where your mother is married to their 3rd cousin, but 600 years is 30 generations, so except for the crossovers, it’s something like 2^30.

    The “Thatcher is related to Reagan”/”Barack Obama has Irish roots” stories have higher probability than the opposite story.

  2. We are all related to either the Biblical Eve, or the modern day Darwinistic seven sisters of Eve, and of course the prolific Genghis Khan.

  3. I don’t know. Mathematically it works, but socially? It doesn’t need Norfolk levels of inbreeding to have a lot fewer than the mathematical number of ancestors once you go back that number of generations.

    Once you go back a few generations, people moved about less. Yes, there were movements and some big movements, but they were the exception rather than the norm. Don’t they say the bicycle dramatically widened the gene pool?

    Plus there are social class factors. Yes there was some breeding across the social divides, but a lot less – it’s certainly not a random pattern. The marriageable group is a lot narrower than would be needed for a random distribution of ancestors.

    Not surprised that these two are related – they’re both upper-middle class and so the social pool is narrower. I’m just not convinced by the “everyone is related” thing.

  4. I think that it is nearer 17,000th cousins rather than 17th if you want to cover the human race. We have developed racial characteristics over tens of thousands of years through the gradual segregation through geographical separation of different gene pools.
    Re the medium-term (600 years) Richard has already said it better than I was going to.

  5. @Richard,

    You don’t need a lot of migration (either geographically or across classes) to get adequate levels of relatedness a few generations later.

    In fact, small migrations, the odd Belgian moving to England in the 16th century type stuff is probably better because individuals have to integrate better than groups do.

  6. Another illustration of just how cynical I am becoming in this modern world.

    I immediately leapt to the conclusion that this was a marketing ploy by the genealogy website Ancestry by providing click bait to the Mail, with the added bonus that it reminded people that gay OCD Aspergy people could have ancestors who could be traced, for a small fee.

  7. Charles OJ, your link to the “most recent common ancestor” being 2,000 to 4,000 years ago says that it is “based on a non-genetic, mathematical model that assumes random mating and does not take into account important aspects of human population substructure such as assortative mating”.

    I’m quite happy to believe the 99,000 to 200,000 years ago estimate, but that’s a lot more than 17 generations back.

  8. “There’s going to be some inbreeding in local areas where your mother is married to their 3rd cousin”: as distinct from those cultures where you will routinely marry a first cousin, I suppose, for generation after generation.

  9. @ Charles OJ
    The wiki article on MRCA is based on arithmetic (not, as it claims, mathematics) and ignores DNA evidence as well as the actual geographical separation of various groups. Inuit and Australian aborigines have no common ancestors in several thousand years unless both are mixed-race due to inter-breeding with Europeans. Many/most Europeans have traces of Neanderthal DNA but black Africans don’t which proves that the groups diverged before the Neanderthals died out about 40,000 years ago.
    So 2,000 to 4,000 is wrong by more than a factor of 10x.

  10. ‘When King James I., in 1603, visited Lumley Castle, Dr. James, Bishop of Durham, wishing to do honour to his friend John, Lord Lumley, gave his majesty a prolix account of his family; but the monarch, having little taste for such details, and growing weary, cut him short with the remark: “Oh, mon, gang na farther; let me digest the knowledge I ha’ gained, for I did na ken Adam’s name was Lumley”‘

  11. Given how small he literate elite was until quite recently I bet they were related more closely, and much more recently. But an earl (even if only of Somerset) gives the story a touch of class.

    Re mitochondrial Eve and Y Adam. I’ve always regarded this as just statistical fluke.

    What are your chances of having a girl, then she having a girl, and so forth for nearly ever. Vanishingly small (but not zero).
    For men having a boy, who has a boy… has in theory the same odds but they get skewed a fair bit by men with harems, more young males than females dying early, etc.

    So no great surprise that Y Adam is a lot more recent than M Eve.

    While the chances are vanishingly small in prospect, in retrospect they are 100%. Your mother had a mother, who had a mother… And your father…

  12. Bloke in Costa Rica

    If we accept that humans are indeed one species (they are, with very low genetic diversity compared to other large mammals) and given that mitochondrial DNA descends through the female line, then mitochondrial Eve necessarily exists. As for the genuine most recent ancestor, I think it’s fair to say that the most recent common ancestor of most of humanity is fairly recent. I can’t remember exactly where I read it (one of Dawkins’, perhaps) but it was to the effect that if a single Portuguese sailor went on shore leave in Marrakesh in 1400 and knocked up a single Moroccan girl, then by now all of Africa is related to all of Europe.

  13. Dearieme:

    “as distinct from those cultures where you will routinely marry a first cousin, I suppose, for generation after generation.”

    Very few generations though, as I reckon genetic mutations will be rampant after a while.

  14. The Industrial Revolution was probably the biggest shake up of the UK gene pool before the mid 20th century. Industrial areas saw huge migrations from both rural areas and abroad. The South Wales industrial area population was about 1/3rd rural Welsh, 1/3rd English migration and 1/3rd Irish.

  15. @Richard

    “I don’t know. Mathematically it works, but socially? It doesn’t need Norfolk levels of inbreeding to have a lot fewer than the m…”

    Hang about.

    Norfolk, you say?

    Inbreeding, you say?

    Norfolk inbreeding?

    By Jove, I’ve think you may have inadvertently hit on the explanation for a chap who has been interesting me (and others) in recent years.

  16. Social divides may be less relevant than you think … there were plenty enough “unofficial” babies from upstairs/downstairs liaisons.

    And, of course, the aristocracy pioneered the concept of mothers having children from several different fathers (again “unofficially”).

    How many generations before all babies are related to at least one member of the Rolling Stones?

  17. Rob: “The Industrial Revolution was probably the biggest shake up of the UK gene pool before the mid 20th century.”

    Factories brought people together from villages. Bicycles, trains and motor cars distributed people more widely.

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